Geographic Range

German cockroaches, believed to have originated in Southeast Asia, are the most widely distributed urban pests. They have been introduced to all parts of the globe including North America, Australia, Africa, and the Oceanic Islands. This ubiquity makes German cockroaches cosmopolitan, with the only deterrent being cold temperatures. ("German Cockroach - Blattella germanica", 2004; Jacobs, 2007)

Habitat

German cockroaches live in temperate or tropical environments. They prefer warm, humid weather and are solely terrestrial. They inhabit a variety of habitats, from very moist areas, such as rainforests and scrub forests, to somewhat drier areas such as taigas and chaparrals. They are also found in sylvatic areas, such as forests and caves, as well as in urban, suburban, and rural settings. Cold is one of the major factors limiting the habitat of German cockroaches. On average, they are found at elevations of 1200 m, and, due to cold temperatures and dryness, they usually do not reside above 2000 m. (Jacobs, 2007; Valles, 2008)

Physical Description

German cockroaches are ectothermic organisms. Adults measure 12.7 to 15.88 cm in length (average 13.0 cm) and weigh between 0.1 and 0.12 g (average 0.105 g). In general, German cockroaches are monomorphic with a flattened, oval shape, spiny legs, and long antennae. They are sexually dimorphic. Males have a thin and slender body, tapered posterior abdomen, visible terminal segments of the abdomen, and do not have tegmina (leathery outer wings). Females tend to be larger and have a stouter body, rounded posterior abdomen, and tegmina covering the entire abdomen. German cockroaches demonstrate bilateral symmetry at all stages of life.

German cockroaches are light brown in color with two broad, parallel stripes on the dorsal side of the body running lengthwise. Nymphal cockroaches resemble adults in shape; however, they are smaller, darker (dark brown to black), have only a single stripe down the dorsal side, and have undeveloped wings. Egg capsules are light tan and round. ("German Cockroach - Blattella germanica", 2004; Day, August 1996; Jacobs, 2007; Valles, 2008)

Development

German cockroaches have three developmental stages: egg, nymph, and adult. Females develop 4 to 8 capsules containing 30 to 48 eggs each in their lifetime. Capsules hatch about 28 days after they begins to form. A few weeks thereafter, a new egg capsule begins to form. The egg stage varies in duration from 14 to 35 days. German cockroaches have 6 to 7 nymphal stages occurring over a period of 6 to 31 weeks. They express incomplete metamorphosis: zygotes develop within eggs and hatch directly into nymphs, which then grow into adult cockroaches. The complete life cycle of the cockroach is roughly 100 to 200 days for females, during which 10,000 descendants of a single cockroach can be produced. (Jacobs, 2007; Kunkel, 2008; McCandless, 2005)

Reproduction

The mating behavior of German cockroaches is driven by pheromones given off by females, which are detected by the antennae of males. German cockroaches breed continuously with many overlapping generations present at any one time. As a result of continuous breeding and promiscuity, population growth has been shown to be exponential. (Jacobs, 2007; McCandless, 2005)

German cockroaches are highly active sexually and breed continuously. Rate of breeding slows only during colder months. They breed throughout the year, mate indiscriminately and do not have cycles. They utilize internal fertilization, and females can store sperm for gradual release. When nymphs develop into adults, they become sexually active almost immediately. Females produce 4 to 6 capsules of 30 to 40 eggs each in their lifetime. Consequently, 3 to 4 generations may live together in a colony. Females lay 120 to 240 eggs per session (average 150 eggs), however, they are iteroparous and have multiple layings. Progeny are dioecious and hatch into nymphs in 25 to 30 days (average 28 days). German cockroaches reach independence between 40 and 150 days of age (average 65). (Kunkel, 2008; McCandless, 2005)

German cockroaches breed continuously year round, though breeding slows during colder months.

Range eggs per season

120 to 240

Average eggs per season

150

Range gestation period

20 to 30 days

Average gestation period

28 days

Range time to independence

40 to 125 days

Average time to independence

65 days

Females German cockroaches carry their eggs on their back for about 6 weeks before they are laid. They hide their eggs in discrete spots, such as cracks, holes, and dark places. They do not, however, provide parental care after eggs are laid. (Day, August 1996; Jacobs, 2007)

Parental Investment

pre-hatching/birth

protecting

female

Lifespan/Longevity

Male German cockroaches, on average, live 100 to 150 days. Females live much longer, with an average lifespan of 190 to 200 days. (Day, August 1996; Jacobs, 2007)

Range lifespanStatus: wild

180 to 200 days

Typical lifespanStatus: wild

100 to 200 days

Average lifespanStatus: wild

140 days

Behavior

German cockroaches usually live in large groups in warm moist areas (such as bathrooms and kitchens). Both nymphs and adults are very motile and generally forage at night. Although members of the same colony forage in similiar areas, they scarcely directly compete for food. German cockroaches are terrestrial and adapted for running. Although they have wings, they cannot fly. (Jacobs, 2007; Kunkel, 2008)

Home Range

German cockroaches do not have a specific home range. They usually dwell in homes and in garbage. (Jacobs, 2007)

Communication and Perception

German cockroaches use their head ganglia to visually perceive their environment. They can also use their subesophageal ganglia to control thoracic fibers, which, when scraped against their body, produce minute noises. This functions as an alarm signal and allows others to escape predation. German cockroaches also use certain pheromones to signal activities such as feeding and evading predators, although these pheromones are generally used to signal mating. (Kunkel, 2008)

Food Habits

German cockroaches often reside in or around human residences due to the accumulation of garbage and detritus. They consume a wide variety of foods, including dead organisms. They usually eat human foods, especially starches, sweets, seeds, grains, grease, and meat products. German cockroaches have also been known to eat soap, toothpaste, and glue. ("German Cockroach - Blattella germanica", 2004; Day, August 1996; Jacobs, 2007)

Predation

German cockroaches are preyed upon by other household pests such as spiders and centipedes as well as domestic pets such as dogs and cats. German cockroaches can re-grow legs when necessary. They prolong their molting cycle to ensure that the new limb grows in during a molt. They also display aposematic coloring in the form of two stripes on their back. German cockroaches are relatively small and are able to hide in small crevices, cracks, and nooks. Nymphs can be as small as 0.7938 mm in width and adults as small as 4.7625 mm. Because of their size and nocturnal habits, they generally do not need to outrun predators. ("German Cockroach - Blattella germanica", 2004; Kunkel, 2008)

Ecosystem Roles

German cockroaches are prey to larger household pests. Because they consume detritus, they aid in the cycling of nutrients. They are also key hosts to parasitic bacteria, protozoans, and viruses, including Blatticola blattae, Hammershmidtiella disingi, Nephridiophaga blattellae, Gregarina blattarum, Lophomonas blattarum, Lophomonas striata, Endolimax blattae, Entamoeba thomsoni, and Nyctotherus ovalis. Some of these parasites utilize humans and other mammals as definitive hosts. (Tsai and Cahill, 1970; Valles, 2008)

Commensal/Parasitic Species

Blatticola blattae

Hammershmidtiella disingi

Nephridiophaga blattellae

Gregarina blattarum

Lophomonas blattarum

Lophomonas striata

Endolimax blattae

Entamoeba thomsoni

Nyctotherus ovalis

Economic Importance for Humans: Positive

There are no known positive economic effects of German cockroaches on humans.

Economic Importance for Humans: Negative

Secretions of German cockroaches produce a foul odor when large colonies have amassed. These can also make human foods unpalatable. This can lead to considerable economic loss, especially in parts of the world where food is scarce or expensive. German cockroaches act as hosts to a number of parasites, such as bacteria, protozoans, and viruses, which lead to human ailments. Fouled food and parasites can lead to food poisoning, dysentery, and diarrhea in humans. Bodies, fragments, waste, and secretions of cockroaches are allergens to humans. These can lead to asthma in young children. Also, German cockroaches may bite humans, feed on particles on sleeping humans, and cause psychological stress. (Day, August 1996; Jacobs, 2007; Valles, 2008)

Contributors

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

Neotropical

living in the southern part of the New World. In other words, Central and South America.

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

detritivore

an animal that mainly eats decomposed plants and/or animals

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scavenger

an animal that mainly eats dead animals

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

vibrations

movements of a hard surface that are produced by animals as signals to others

Tsai, Y., K. Cahill. 1970. Parasites of the German Cockroach (Blattella germanica L.) in New York City. The Journal of Parasitology, 56(2): 375-377.
Accessed
December 05, 2008
at http://www.jstor.org/pss/3277678.

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
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Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.